1. Field of the Invention
This invention relates to railway tank cars and more specifically, to a split skid protection casting and insert adapter for replacement outlet valve of a tank car.
2. Summary of the Prior Art
Railway tank cars are commonly utilized for transporting bulk freight in liquid or semi-liquid form. A large number of the commodities transported by tank cars fall within the government classification of hazardous materials. The commodity carried in the tank car is discharged through an outlet extension nozzle that is connected to the outlet valve mounted at the bottom of the tank.
The bottom outlet valve and outlet extension nozzle create discontinuities or protuberances at the bottom of the tank car. The presence of such a discontinuity, if not protected, raises the risk that the protruding structure, particularly the bottom outlet valve, will rupture in a disrailment situation by impacting against the rail or other surface. As a result of this potential hazard, the Association of American Railroads (A.A.R.) has specified that the bottom fittings for discharge be equipped with a bottom protection device, commonly referred to as skids, that prevent undesired discharge of the commodities upon derailment. An example of a prior protection device in the form of a skid is disclosed in U.S. Pat. No. 4,697,528 issued Oct. 6, 1987 to R. E. Rehbein.
In recent years it has become advantageous to replace existing bottom outlet valves of tank cars in service with newer more efficient bottom outlet valves. For example, relatively older tank cars are equipped with a bottom outlet valve manufactured by ACF Industries, Inc., known as an ACF Low Profile 6" Bottom Operated Outlet Valve. It is advantageous to retrofit such existing outlet valves with more efficient bottom outlet valves, such as, for example, a Jamesbury Low Profile Bottom Outlet Valve (4" AZFRC, Mod. B).
Several problems are associated with prior techniques of retrofitting a bottom outlet valve to a tank car that make known replacement methods a relatively difficult and expensive task. Current procedures for retrofitting bottom outlet valves on tank cars require an opening be made in the tank shell with the result that stress relieving (post weld heat treatment) and internal bracing must be done, which is a time consuming and costly procedure. When stress relieving a car, moreover, it disadvantageously elevates the temperature of the tank car shell, thus causing damage to paint and interior lining. Accordingly, it is desirable to provide improved devices and methods by which a more efficient bottom outlet valve is retrofitted on an existing tank car without the requirement of stress relief of the tank shell and the problems associated therewith.